Monthly Archives: May 2013

The JPL Horizons ephemeris system

One of the challenges of the amateur-DSN stations to track planetary and solar system space-probes is the position and frecuency accuracy. Currently all the stations are using the ephemeris provided by the JPL Horizons system. This is a cool system and can be used online using telnet, using a web interface or via email and provide-us the position, range and deldot of the select target, then using this data can track easy the probes and calculate the doppler.

JPL Horizons

JPL Horizons

Due that the JPL Horizons is a service for the main public basically for amateurs and space anthussiastas, they can not provide ephemeris for probes or missions that are orbiting a planet because this kind of missions not are static and depends of the stage of the mission.

The solution provided by Horizons is track the planet is orbiting the probe, for example to track MRO, MEX and MO have to track Mars. It works because the position difference is minimal, a typical difference of less of 0.05 deg and it not makes a sense in our small dishes. The amateur-DSN members are detecting space propbes that are orbiting a planet during years with good results, but we have some troubles like taht we dont know when the probe is eclipsed by the planet and, and we dont know the exact frequency where is the probe, because the probe and planet have a differnt deldot. Now I’m working in generate my own ephemeris, to get the data of the probes that are orbiting planets.

A interesting issue about Horizons that I discovered recently is that dont give the data in UTC time, it gives the data in Barycentric Dynamical Time.

New mixer for the 8.4 GHz downconverter

Today I continued updating the downconverter for X-band deep space probes. Having the local oscillator selected, today was the mixer selection. Up today I was using a RHG mixer purchased in 2006, but from the 2006 up today I purchased another units, but not tested up today.

RF Mixer testing, test setup

RF Mixer testing, test setup

After test the 5 units, looks that I have a unit perfect for 8.4 GHz 🙂 it is a Aertech 8500 this mixer look more of 4 dB better that the RHG mixer used up today.

RF Mixer comparation

RF Mixer comparation

Now only need check the low noise amplifier to see the performance and decide if I build a new one.  I’m very anxious to receive space probes again!